The angle of attack is of primary concern in the operation of aircraft wings, during both take-off and landing, and during flight as well. In conventional aircraft having a tail section and empenage control surfaces, the wing is attached at a positive four or five degree angle relative to the fuselage and normal trim plane of the horizontal stabilizer. However, in "flying wing" and "span loader" type aircraft devoid of tail sections and rearwardly extended empenage control surfaces there is an inherent absence of means to establish the most necessary moment of force required to controllably vary the angle of attack. Therefore, the line and force of thrust has been employed to implement increased angle of attack attitudes, but with tragic results as when a nose-down attitude is accompanied with too great an air speed; in which case flying wing aircraft have failed when the pilots were unwaringly and/or unavoidably entrapped in such situations. Accordingly, it is a general object of this invention to provide means by which downward force is applied to flying wing or span loader aircraft to controllably increase the wing angle of attack, to control roll, and to control direction, thereby establishing attitude changes and lift as circumstances require.
Span loaded flying wings have great advantages over conventional fuselage aircraft, having reduced parasite drag for increased speed, range and high performance characteristics. Also, load distribution throughout the wing configuration has its structural advantages. Flight control is executed in a normal fashion and differs from conventional aircraft only in a minor degree, utilizing for example, flaps to produce drag at the wing tip in place of a rudder per se. In practice the rudder flaps have formed a portion of the "trim flaps" and which are loacted at the wing tips and adjusted up or down to trim the aircraft longitudinally to the desired angle of attack attitude. Maneuverability of the flying wing is by means of "elevons" combining the functions of elevator and aileron and located along the trailing edge inboard of the aforesaid trim flap. Additionally, landing flaps are employed inboard of said ailerons and/or elevons. A characteristic of the said trim flap control is its "spoiler" effect which disturbes air flow over the upper camber of the wing and reduces lift. Therefore, greater wing area is required while the trim effect is restricted by the closely coupled moment arm over such trim flaps as related to the center of lift of the wing. Accordingly, it is an ofject of this invention to provide means to remove air flow disturbances from the wing surfaces and to increase the moment arm effectiveness of reactive air control surfaces, in order to control the positive angle of attack and direction of flight, as may be required.
The necessity of controlled angle of wing attack cannot be over emphasized, for optimum take-off characteristics, for in-flight attitude corrections and altitude changes, and for landing characteristics as well. For example, on take-off there are two distinct speed conditions; V1 which is the speed at which flight is committed, taking into account all factors including load, runway length, altitude, wind, temperature and pressure, and obstacles etc.; and V2 which is the speed at which the aircraft is to be rotated into a climbing attitude. It is the transistion between wing attitudes complying with these two speed conditions with which this invention is concerned on take-off, and landing as well. In flight and on landing, this invention is concerned with wing attitude adjustability without resort to changes in thrust, and especially without the requirement of increasing thrust. For example, angle of wing attack is not to be increased in reliance upon an increase in thrust; and on the contrary is increased independent of thrust applied. Accordingly, it is another object of this invention to provide control surfaces independent of the thrust applied and which determines the positive angle of wing attack, whereby transistion from a V1 condition into a V2 condition can be effected to rotate the aircraft on take-off, and to advantageously apply a nose-up attitude in flight and at lower speeds for landing.
In carrying out this invention there are retractile control surfaces that extend into clear air separated from the supporting wing camber (top and bottom). In practice, extension of said control surfaces increases their angle of deflection to establish controllable downward thrust at the trailing edges of the wing (left and right). The lever effect with respect to the center of lift is enhanced by the swept wing configuration, applying a downward force that rotates the wing to increase the angle of attack. Simultaneously there is turbulant airflow around said control surfaces, creating the desirable drag for controlling air speed and directional stability. It is therefore an object of this invention to provide a simple and rugged structural form of means inherently balanced and requiring minimum force application for its operation.